HK1079494B - Unit for sterilizing webfed material on a machine for packaging pourable food products - Google Patents

Description

Device for sterilizing web-fed material on a machine for packaging pourable food products

Technical Field

The present invention relates to a device for sterilizing on a machine a web of material for packaging a supply of pourable food products.

Background

Various machines are known for packaging pourable food products, such as fruit juice, wine, tomato sauce, pasteurized or long-storage (UHT: ultra high temperature sterilized) milk, etc., on which the packages are made from a continuous tube of packaging material consisting of a longitudinally sealed sheet.

The packaging material has a multilayer structure comprising a layer of paper material covered on both sides with a heat-sealing material, for example polyethylene. And in the case of aseptic packages for long-storage products, such as UHT milk, the packaging material comprises a layer of barrier material, for example constituted by an aluminium foil, which is superimposed on a layer of heat-seal plastic material and in turn is covered with another layer of heat-seal plastic material eventually constituting the inner face of the package and thus contacting the food product.

To produce a sterilization wrap, the web of packaging material is unwound off a reel and fed through a sterilization device in which the web is sterilized, for example by immersion in a bath of liquid sterilizing agent, such as a concentrated solution of hydrogen peroxide and water.

More precisely, the sterilizing device comprises a bath which, in use, is filled with a sterilizing agent, in which bath the web is continuously fed. The bath conveniently comprises two vertical parallel branches joined at the bottom to form a U-shaped path long enough to ensure that the packaging material has been treated for a sufficient time. In order to perform an effective treatment in a relatively short time, and thus to reduce the size of the sterilization chamber, the sterilization agent must be maintained at an elevated temperature, for example about 70 ℃.

The disinfection device further comprises: a treatment chamber located above the bath, in which the packaging material web is dried; and a sterilization chamber in which the web is folded and sealed longitudinally to make a tube, which is then continuously filled with the product to be packaged.

More precisely, in the treatment chamber, the web is treated to remove any residual sterilizing agent, the permitted amount of which in the packaged product is governed by strict standards (maximum permitted amount in the range of a few parts per million).

This treatment typically involves mechanically removing any droplets from the material, followed by drying with air.

The droplets may be formed, for example, by feeding the material through a pair of wringing rollers which are conveniently located in close proximity to the treatment chamber inlet, with the material still being covered downstream of the inlet by a film of disinfectant, but without visible droplets.

Drying may be accomplished by means of air knives facing the two opposite surfaces of the material, which air knives are supplied with air from the sterile environment, for example by means of ｃA recirculation duct as described in EP- ｃA-1050467, which recirculation duct is arranged to remove residual traces of disinfectant by evaporation.

Alternatively, complete drying may be achieved in a lower drying tunnel through which the process chamber communicates with the sterilization chamber.

Before leaving the sterilization chamber, the sheet is folded into a cylinder and sealed longitudinally to form a continuous, longitudinally sealed, vertical tube in a known manner. In other words, the tube of packaging material constitutes an extension of the aseptic chamber and is continuously filled with the flowable food product and then fed to a form-sealing (cross-sealing) device, on which it is gripped and cross-sealed between pairs of jaws to make the aseptic pillow packs, to make the single packs.

The pillow packs are separated by cutting the seal between the packs and are fed to a final folding station where they are folded mechanically into the final shape.

Packaging machines of the above type are widely used and can meet a wide range of food industries which produce sterile packages from sheet-supplied packaging material. In particular the performance of the sterilizing unit ensures that the standards governing the sterilization of the packages are fully met.

However, there is a need for further improvements within the industry itself, in particular with regard to pressure control in the disinfection device.

In known machines, the pressure and temperature conditions in the treatment and sterilization chamber are generally controlled by a closed air treatment circuit which draws air from the chamber and supplies it back into the chamber.

To ensure the sterilization of the environment formed by the treatment and sterilization chambers, both chambers must be maintained at a pressure higher than atmospheric pressure, so that any leakage can only occur outwards, i.e. leakage of sterile air from the machine, but no non-sterile air can escape from the outsideThe environment leaks into the machine. In addition, to ensure a one-way air flow from the sterilization chamber to the treatment chamber, at least about 10mmH must be maintained between the two chambers₂Pressure difference of O.

In the known machines, this pressure value in the sterilisation treatment chamber is substantially determined by the constructional conditions and guaranteed by suitable calibrated leakages between the two chambers and between the treatment chamber and the outside, and is simply monitored, so if they are too low, for example due to sealing defects in the application, the machine must be stopped and therefore production must be stopped in order to take the required steps.

Disclosure of Invention

It is an object of the present invention to provide a device for sterilizing packaging material which is constructed to eliminate the above-mentioned drawbacks, i.e. which is arranged to control the pressure in the sterilization chamber and the treatment chamber without stopping the production.

According to the present invention, there is provided a sterilizing device for sterilizing a sheet of packaging material on a machine for packaging pourable food products, the sterilizing device comprising:

a bath containing a disinfectant, in which bath the web is continuously fed;

a sterile environment, the sterile environment comprising: a treatment chamber connected to an outlet of the bath and housing drying means for removing residual sterilant from the web; and a sterilisation chamber communicating with said treatment chamber via an opening for passing said sheet, in which said sheet is folded and sealed longitudinally to make a tube which is continuously filled with a packaged product; and an air treatment circuit for controlling the treatment conditions in said sterile environment, comprising suction means for drawing air from said treatment chamber, air treatment means and means for feeding treated air into said sterilization chamber;

the method is characterized in that: comprising valve means interposed between said treatment chamber and suction means of said air treatment circuit, and which can be actuated during operation of said machine to control the pressure conditions in said sterile environment.

In a preferred embodiment of the present invention, the sterilizing device comprises: a transition chamber in communication with the inlet of the bath and with the suction device; and a valve arrangement comprising an orifice interposed between the process chamber and the transition chamber; and a closure member which is movable to adjust the opening of the aperture between the two chambers and thereby adjust the pressure in the sterile environment during production.

Preferably, the shutter is movable between an open position and a fully closed position, the fully closed position isolating the process chamber from the external environment; thus during production pauses air can be drawn through the bath, which is empty during the pauses. This is provided for ventilating and cooling the packaging material, so that the impregnation of the edges of the web with sterilizing agent is reduced when the production is started again.

A partition is arranged between the treatment chamber and the sterilization chamber to ensure a pressure difference between the two chambers and to form an opening between the two chambers through which the packaging material is supplied.

According to a further characteristic of the invention, said opening is asymmetrical with respect to the plane of movement of the packaging material, i.e. the opening is higher at the side facing one of the two surfaces of the material, and preferably at the lower side.

In this way, the sterilizing device can also be used for treating packaging material provided with opening devices which are fed through the upper side of the opening, while the other lower side ensures a sufficient pressure drop between the two chambers.

Preferably, the packaging material is fed horizontally through the opening and is then guided by a roller accommodated in the sterilization chamber, which roller is located immediately downstream of the opening; and the opening is formed on the upper side, for example downwards, by a partition which is made close to the roller in order to define a barrier ensuring the desired pressure drop for the air flow from the sterilisation chamber to the treatment chamber.

Drawings

Preferred non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:

fig. 1 is a diagrammatic view of a machine for packaging pourable food products, and having a sterilizing device according to the present invention; and

figures 2 and 3 show a partial sketch of a disinfection device according to the invention in two different operating conditions.

Detailed Description

Number 1 in fig. 1 indicates as a whole a machine for packaging pourable food products and for continuously producing aseptic packages of pourable food products from a sheet-fed packaging material 2 (hereinafter referred to simply as "sheet 2").

The machine 1 comprises sterilizing means 3 for sterilizing the web 2, and the web 2 is fed to the sterilizing means 3 along path P1 from a roll (not shown).

The machine 1 further comprises means 4, upstream of the sterilizing device 3, for providing the web 2 with closable opening devices 5, while the means 4 are conveniently constituted by a known injection-moulded plastic station and feed the web 2 stepwise by means of the means 4. On leaving the means 4, the sheet comprises, one after the other, equally spaced opening means 5 (only shown schematically in figure 1 on a portion of the sheet), the opening means 5 projecting from one face of the sheet 2.

The sterilizing device 3 comprises: a transition chamber 6 into which the web 2 is first fed; a sterilizing bath 7 which is7 contains a liquid disinfectant, such as 30% hydrogen peroxide (H)₂O₂) With water, web 2 is fed through sterilizing bath 7; and a treatment chamber 8, in which treatment chamber 8 the web 2 is dried, as will be explained in further detail below.

Bath 7 is substantially constituted by a U-shaped duct which, in use, is filled to a predetermined level with disinfectant, and which in turn is constituted by two vertical inlet and outlet branches 9, 10, respectively, branch 9, 10 having respective top openings 11, 12, top openings 11, 12 constituting the inlet and outlet, respectively, of web 2 of bath 7 and communicating with transition chamber 6 and process chamber 8, respectively. The two branches are connected at the bottom by a bottom portion 13 of bath 7, in which bottom portion 13 horizontal transport rollers 14 are housed.

Inside bath 7, web 2 thus moves along a U-shaped path P2, the length of U-shaped path P2 being configured to ensure that the length of the packaging material is sufficient to remain in the sterilizing agent.

The bath 7 is connected to a known peroxide control loop 15 (not described in detail) and is maintained, in use, at a controlled temperature, for example about 70 ℃.

A treatment chamber 8 (figures 2 and 3) is located above the transition chamber 6, separated from the transfer chamber 6 by a partition 16, and houses drying means, indicated as a whole by 17, and for removing residual sterilizing agent from the web 2.

The drying device 17 comprises two parallel, horizontal, idle wringing rollers 18, at least one of which is covered with a relatively soft material, located on opposite sides of the web 2 adjacent the inlet of the treatment chamber 8, the rollers 18 cooperating with respective opposite surfaces of the web 2 and exerting pressure thereon to squeeze out any drops of disinfectant and return it to the bath 7.

The wringing rollers 18, as illustrated in EP- ｃA-1050468, conveniently each comprise ｃA small-diameter intermediate portion (not shown) corresponding to the longitudinal intermediate portion of the sheet 2, to allow the opening devices 5 to pass without interfering with the rollers.

Downstream of the wringing roller 18, the sheet 2 is deflected (changes direction) along a horizontal path P3 by the conveying roller 19.

The drying means 17 also comprise a so-called "air knife" 21 (schematically indicated), known per se, the air knife 21 being constituted by a nozzle 22 for directing a jet of air onto the surface of the sheet 2 which, in use, eventually constitutes the inside of each package, and by two plates 23 for directing, in use, the jet of air substantially parallel to the direction of movement of the sheet 2, but in the opposite direction of this movement.

The nozzles 22 form part of an air handling circuit 24, the circuit 24 being described in further detail below.

The sterilizing device 3 further comprises: a vertical sterilizing chamber or tower 25 having a top 26 communicating with the treatment chamber 8 through an opening 27, the opening 27 being for the passage of the web 2; and an elongated bottom 28, in which bottom 28 sheet 2 is folded longitudinally into a cylinder and sealed longitudinally to make a continuous tube 29 of packaging material having a vertical axis a. The sterilisation chamber 25 together with the treatment chamber 9 thus constitutes a sterilisation environment 30.

The top 26 houses several conveying and guiding rollers 31, 32, 33 for guiding the sheet 2 from a horizontal path P3 to a vertical path P4 parallel to the axis a of the tube 29. More precisely, the roller 31 is powered and located immediately downstream of the opening 27; the roller 32 is idle and constitutes a tensioner; while roller 33 is also idle and is provided for guiding and deflecting web 2 downwards.

The tube 29, made downstream of the roller 33 in a known manner not depicted, is filled continuously with product through a filling duct 34 and fed out downwards through a bottom opening 35 in the sterilisation chamber 25, thus actually constituting an extension of the sterilisation chamber.

The machine 1 comprises known forming and transverse sealing means 36 (not shown in detail), in which means 36 the tube 29 of packaging material is gripped and transversely sealed by pairs of jaws 37 to make sterile pillow packs 38, these pillow packs 38 being finally cut and folded in a known manner to make the single packages.

The air handling circuit 24 comprises: a suction duct 40 communicating with the transition chamber 6; and a known treatment device 41 (not shown in detail), the device 41 having an inlet connected to the conduit 40 and an outlet connected to the conduit 42 for feeding treated air into the sterilizing device 3. The processing means 41 conveniently comprise, in a known manner: a compressor 43; a cleaning device 44 for removing residual disinfectant; and a heating device 45 that heats and sterilizes the air. The conduit 42 is connected to an inlet of a three-way distributor 46, the distributor 46 having two outlets 46a, 46b, the outlets 46a and 46b being connected to the nozzles 22 of the air knives 21, respectively, by a conduit 47, and to one or more air inlets 48 in the bottom part of the sterilization chamber 25 by a conduit 49. The distributor 46 has two throttle plates 50, 51 which can be operated independently, for example by means of respective servo cylinders (not shown), and which are provided for controlling the air flow along the conduits 47, 49; an electric heater 52 is accommodated in the duct 47.

The transition chamber 6 communicates with the external environment through an orifice 53; the orifice 53 has a lid normally closed by gravity, but it is opened at low pressure during the operation of the machine, while for the circuit 24 the orifice 53 constitutes a zero-pressure reference point with respect to the external environment.

The process chamber 8 can communicate with the transition chamber 6 via an orifice 54, which orifice 54 can be adjusted by means of a throttle plate 55.

The shutter 55 moves-for example, rotating integrally with a pin 56 controlled by an actuator 57-between an open position (figure 2), in which the process chamber 8 is in direct communication with the transition chamber 6, and a closed position (figure 3), in which the two chambers are isolated. The open position can be conveniently adjusted, for example, by manually adjusting the mechanical limit stop 58 of the throttle plate 55 even during operation of the machine.

The pressure in the sterilization chamber 25 is sensed by a sensor PS1 with a readout 59.

When web 2 is provided with opening devices 5, opening 27 between chamber 8 and sterilization chamber 25 must be high enough on the underside of web 2 where opening devices 5 project to allow passage therethrough. To prevent the opening 27, whose height is arranged as described above, from causing the pressure in the sterilisation chamber 25 to be substantially equal to that in the treatment chamber 8, the opening 27 is asymmetrical with respect to the plane of the web 2, but has a minimum height upwards and is delimited downwards by a baffle 60, which baffle 60 is configured close to the roller 31 so as to constitute an air flow barrier and thus determine a concentrated pressure drop.

The programmable control means 61 of the machine 1 control the process parameters of the sterilizing device 3, and in particular the heating means 45 of the air treatment device 41, the peroxide control circuit 15, the distributor 46, the heater 52 and the actuator 57, on the basis of predetermined reference values for each operating phase of the machine.

The process parameters are different variables for different working stages, which are determined, for example, in the following manner: the temperature of the air from the device 41 detected by the first detector TS 1; the temperature in the top 26 of the sterilisation chamber 25 detected by the second detector TS 2; and the air temperature in conduit 47 downstream of nozzle 22 as detected by a third detector TS 3.

The operation of the sterilizing device 3 will now be described with reference to two typical operating conditions (production and short standstill of the machine 1).

During production (fig. 2), bath 7 is filled with sterilising solution, and web 2 is fed through the bath, dried in treatment chamber 8 and sealed longitudinally in the tube of sterilisation chamber 25.

Under the above operating conditions, the distributor 46 is arranged to partially close the outlet 46b connected to the duct 49 so as to supply to the nozzle 22 a basic flow portion, for example 40%, and the remaining portion, for example 60%, to the sterilisation chamber 25. The air temperature at the outlet of the device 41 is set at about 120 c and the heater 52 is controlled on the basis of feedback from the sensor TS3 to supply air to the nozzle 22 at about 180 c.

Keep throttle plate 55 open, and so processThe chamber 8 is in direct communication with the suction duct 40 of the air treatment circuit 24; when the throttle plate 55 is opened, the flow cross-section of the opening 27 and the orifice 54 has the dimensions: maintaining a pressure in the processing chamber 8 of about 10-20mmH₂O, and about 20-30mmH in the sterilization chamber₂O while the pressure drop through the opening 27 is about 10mmH₂O。

The above overpressure values with respect to the atmosphere are sufficient to prevent the ingress of external agents, but low enough to prevent substantial leakage of disinfectant contaminated air from contaminating the workplace. The pressure drop through the opening 27 ensures a continuous one-way flow from the sterilisation chamber 25 to the treatment chamber 8.

The pressure in the sterilization chamber 25 during production is detected by the sensor PS 1.

When the pressure in the sterilisation chamber 25 drops towards a minimum safe value, for example due to a poor seal, it is possible to adjust during production by manually adjusting the limit stop 58, in fact by reducing the flow section of the orifice 54.

During short production pauses due to any routine maintenance of machine 1, web 2 is stopped from being fed and bath 7 is emptied.

In this condition, the dispenser 46 is set to fully open the outlet 46b and partially close the outlet 46a, so that the fluid is supplied substantially entirely to the sterilization chamber 25, with a minimum portion of about a few percent being supplied to the air knife 21.

Due to its high temperature inertia, the sterilisation chamber 25 acts as a cooler for the air flowing through it and through the opening 27 into the treatment chamber 8; and, as the aperture 54 is closed, the cooled air moves along the empty bath 7 to the transition chamber 6 where it is extracted. This "venting" of the bath cools web 2 and reduces the so-called "edge wicking phenomenon" -the staining of the edges of web 2 by the sterilizing agent, when bath 7 is refilled to start the machine. By lowering the temperature of the bath 7 by means of the venting effect described above and by filling the disinfectant at a suitably high temperature when the machine is started, edge wicking, which occurs at the exposed edges of the web 2 of paper layers, is substantially reduced.

Clearly, changes may be made to machine 1, and in particular to disinfection device 3, without, however, departing from the object of the accompanying claims.

In particular, the orifice 54 cross-section can be automatically closed-loop controlled to compensate for any pressure drop in the sterilization chamber 25.

Claims (11)

1. Sterilizing unit for sterilizing a web (2) of packaging material for packaging pourable food products on a machine, the sterilizing unit (3) comprising:

a bath (7), the bath (7) containing a disinfectant, the web (2) being continuously fed in the bath (7);

a sterile environment (30), the sterile environment (30) comprising: a treatment chamber (8), the treatment chamber (8) being connected to the outlet (12) of the bath (7) and accommodating drying means (17) for removing residual sterilizing agent from the web (2); and a sterilisation chamber (25), the sterilisation chamber (25) communicating with said treatment chamber (8) through an opening (27), the opening (27) being intended to pass through said sheet (2), while in the sterilisation chamber (8) said sheet (2) is folded and longitudinally sealed to make a tube (29), the tube (29) being continuously filled with the product to be packaged; and

an air treatment circuit (24), the circuit (24) being for controlling process conditions in the sterilization environment (30) and comprising: -suction means (40) for drawing air from the treatment chamber (8), air treatment means (41) and means (42, 47, 49) for feeding treated air into the sterilisation chamber;

characterized by comprising valve means (54, 55) interposed between said treatment chamber (8) and said suction means (40) of said air treatment circuit (24), while valve means (54, 55) can be actuated during operation of said machine (1) to control the pressure conditions in said sterile environment (30).

2. A disinfection apparatus as claimed in claim 1, and comprising a transition chamber (6) communicating with an inlet (11) of the bath (7) and with said suction means (40); the valve means (54, 55) are interposed between the treatment chamber (8) and the transition chamber (6).

3. A disinfection apparatus as claimed in claim 2, characterized in that said valve means (54, 55) comprise: an orifice (54) connecting said process chamber (8) to said transition chamber (6); and a movable throttle plate (55) for adjusting the opening of the small hole (54).

4. A disinfection apparatus as claimed in claim 3, characterized in that a shutter (55) is movable between an open position, in which said treatment chamber (8) communicates directly with said transition chamber (6) via said aperture (54), and a closed position, in which said treatment chamber (8) communicates with said transition chamber (6) via said bath (7) when said bath (7) is not containing a disinfectant.

5. A disinfection apparatus as claimed in claim 4, comprising: a sensor (PS1) for detecting a pressure in the disinfection environment (30); and adjusting means for adjusting the position of said opening to maintain the pressure in said sterile environment (30) at least equal to a predetermined limit value.

6. A disinfection device as claimed in any one of the preceding claims, comprising barrier means (60) for creating a local pressure drop between said disinfection chamber (25) and said treatment chamber (8); the barrier means (60) constitute the opening (27) between the treatment chamber (8) and the sterilization chamber (25), the web (2) being fed through the opening (27).

7. A sterilising apparatus as claimed in claim 6, for treating a web (2) of packaging material provided with opening means (5) projecting from one surface of said web (2); the method is characterized in that: the opening (27) is asymmetrical with respect to the plane of movement of the sheet (2), and the opening (27) is higher on the side facing the surface of the sheet (2) from which the opening means (5) project, with respect to the other side of the opening (27).

8. A disinfection device as claimed in claim 7, characterized by comprising a guide roller (31) located immediately downstream of said opening (27); the baffle means comprises a baffle (60) constituting the opening (27), and the baffle (60) is shaped close to the roller (31).

9. A disinfection apparatus as claimed in claim 1, characterised in that said drying means (17) comprise at least one nozzle (22) for directing a jet of air onto said web (2); said means for feeding treated air into said sterilisation chamber (30) comprise: a first conduit (49) supplying air to an air inlet (48) of said sterilisation chamber (25); a second conduit (47) supplying air to said nozzle (22); a distributor (46) having an inlet connected to the air treatment device (41); and two outlets (46a, 46b) connected to the second conduit (47) and the first conduit (49), respectively.

10. A disinfection device as claimed in claim 9, comprising a heater (52) accommodated in said second conduit (47).

11. A disinfection device as claimed in claim 2, comprising an aperture (53) connecting said transition chamber (6) to the external environment; the orifice (53) is normally closed by gravity, but is opened during operation of the machine.